Prenatal diagnosis of mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis in a pregnancy with a favorable outcome.

We present prenatal diagnosis of mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis with a favorable outcome. A 23-year-old woman underwent amniocentesis at 24 weeks of gestation because of congenital bowel dilation in the fetus. Amniocentesis revealed a karyotype of 48,XX,+11,+12[1]/46,XX[24]. In 25 colonies of cultured amniocytes, all five cells in one colony had the karyotype of 48,XX,+11,+12, while the rest 24 colonies had the karyotype of 46,XX. The parental karyotypes were normal. Repeat amniocentesis was performed at 26 weeks of gestation. Interphase fluorescence in situ hybridization (FISH), array comparative genomic hybridization (aCGH) and quantitative fluorescent polymerase chain reaction (QF-PCR) were applied on the uncultured amniocytes, and conventional cytogenetic analysis was applied on cultured amniocytes. Interphase FISH analysis showed no trisomy 11 signal and no trisomy 12 signal in 102 uncultured amniocytes. QF-PCR analysis excluded uniparental disomy (UPD) 11 and UPD 12. aCGH analysis showed no genomic imbalance. The cultured amniocytes at repeat amniocentesis had the karyotype of 46,XX in 13/13 colonies. At term, a healthy 3445-g female baby was delivered with no phenotypic abnormality except imperforate anus and a perianal fistula. The cord blood had a karyotype of 46,XX in 40/40 lymphocytes. Postnatal interphase FISH analysis of buccal cells and urinary cells revealed trisomies 11 and 12 signals in 11/111 (9.9%) buccal cells compared with 3% in normal control, and in 3/103 (2.9%) urinary cells compared with 0.98% in normal control. Mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis without UPD 11 and UPD 12 can be associated with a favorable outcome.

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